Magnetic Separation News, 1986, Voi. 2, pp. 71-840731-3632/86/0202-0071 $25.00/0) 1986 Gordon and Breach, Science Publishers, Inc.Printed in the United Kingdom

MAGNETIC SEPARATION IN ROMANIA

NICOLAE REZLESCU, ELENA-BRANDUSA BRADU, GHEORGHE IACOB,VASILE BADESCU and LAVINIA IACOBCentre of Technical Physics, Jassy, Romania.

Abstract The utilization of the magnetic separators offoreign and Romanian source is presented and the mostimportant achievements in research, engineering design andmanufacturing activity concerning the magnetic separationin Romania are reviewed.

INTRODUCTION

Magnetic separation in Romania, as a technological process and as

a research and designing activity, must be considered in close

connection with the economic and industrial development of the

country. Before World War II, Romania was a poorly developed

country. In the post-War period industrial development of the

country was the main concern of the Romanian government and

people.

Initially, this development was based on a massive import

of technology from more industrially advanced countries. Now-

adays industrial development is much less dependent upon external

influences, so much so that there is world-wide recognition of

many proprietary products of Romanian industry.

In this connection, magnetic separation in Romania may be

considered as existing only since 1945. Until 1970, there

existed only magnetic separation systems imported as part of a

technological package. Thus, we find magnetic separators

included in flow sheets from the extractive industry and ore

processing, in metallurgy, food or chemical industries, cellulose

71

72 N. REZLESCU ET AL.

and building material industries.

After 1970, with the setting up of large research and

engineering design centres, a wide range of subjects was invest-

igated with connections in magnetic separation, including optim-

ization of already existing processes, studies on the feasibility

of magnetic separation methods in processing low grade ores and

other materials, researches concerning the theoretical bases of

the separation methods and the designing and manufacturing of

modern separators.

In this connection, an important part is played by the

Centre of Technical Physics of Jassy (C.T.F.), the Research

Institute for Electrotechnical Industry of Bucharest, the

Research and Engineering Institute for Non-metallic Substances

and Minerals of Cluj-Napoca, the Mining Research and Engineering

Institutes of Deva and Baia Mare, Polytechnical Institutes of

Jassy and Timisoara, and the Mining Institute of Petrosani.

In the following, we shall present in brief the applica-

tions of magnetic separation in Romanian industry, emphasizing

the main areas benefittin from this technology, as well as themain types of magnetic separators in use and some of the more

significant results obtained in research and engineering activ-

ity of the Romanian institutes.

MAGNETIC SEPARATION IN INDUSTRY

Almost all industries processing raw materials have flow sheets

which include magnetic separation. This is necessary for the

purification of various materials by removing the ferro- and

paramagnetic bodies or thin particles or for the beneficiation

of other materials, the magnetic product being used in this case.

Most of the magnetic separators are of foreign source, being

imported from the Soviet Union, Czechoslovakia, East Germany,

West Germany, Italy, Sweden, the United States. There is a large

MAGNETIC SEPARATION IN ROMANIA 73

variety of such devices, including:

Magnetic plates with permanent magnets or electromagnets,

used in the food industry (for cereals processing), cellulose

industry, chemical or coke industry. These are designed to pick-

up tramp metals which are then removed manually.

Belt magnetic separators used for picking-up tramp ferro-

magnetic bodies, for the purification of useful materials by

removing the magnetic particles (as railings) or for obtaining

magnetic concentrates (in iron ore processing, iron extraction

from the blast furnace slags and so on).

Dry drum magnetic separators, used as above.

-Wet drum magnetic separators, in the three principal

versions- counter-current, counter-rotating and noncurrent.

These are mainly used for iron ore concentration or in the chem-

ical industry.

Iron ore upgrading by means of wet drum magnetic separators

is preceded at Teliuc-Hunedoara by the magnetizing roasting,

extractions of more than 85 percent being obtained. These sep-

arators are also used for magnetite extraction from the copper

ore flotation railings (at the preparation stations in Maramures

and Dobregea), from blackstone ashes (at the power plants), as

well as from red bauxite slime. In coal processing with heavy

liquids, the recovery and regeneration of magnetite or ferro-

silicon is also done by means of wet drum magnetic separators.

The wet and dry drum magnetic separators include both

imported devices and those designed and manufactured in

Romania.

Magnetic induced-roll separators are mostly used in ore

processing and in the chemical industry. In dry processing they

are found in quartz sand purification by iron oxide removal (in

the glass industry) and in rare mineral concentration. Along

with imported installations of this kind, whole lines of

Romanian induced roll magnetic separators have been introduced,

74 N. REZLESCU ET .AL.

modernized and optimized. Wet magnetic induced roll separators

are largely utilized, especially for iron and manganese ore up-

grading.

-High gradient magnetic separators were recently introduced

into Romanian industry. They have already become the favourite

tools of the kaolin and clay industries being utilized for deferr-

ization and for increasing brightness. A SALA-type HGMS device

has been installed at Rebrisoara mine, successfully processing

the local kaolin. Romanian HGMS separators are also working in

Romanian industry.

RESEARCHES CONCERNING THE PHYSICS AND TECHNOLOGYOF MAGNETIC SEPARATION

An important part in tackling research problems in Romania con-

cerning magnetic separation is played, first of all, by two

research institutes: the Centre of Technical Physics of Jassy,

which is mainly concerned with the physics and technology of

magnetic materials and phenomena, and the Research Institute for

Electrotechnical Industry, which deals with the study and design

of electromagnetic machines and devices. At the same time, an

important role is played by the Mining Research and Engineering

Institutes of Deva, Cluj-Napoca and Baia Mare, sponsored by the

Ministry of Mines.

The problem of magnetic separation of materials is also

dealt with by some Romanian institutes of higher technical

education, as the Polytechnical Institutes of Jassy and Timisoara,

the Mining Institute of Petrosani and some others. Their efforts

are directed toward the optimization of already-existing magnet-

ic separation processes, with a view to reducing their energy

consumption and increasing their efficiency, studying the feas-

ibility of magnetic separation methods for a large range of use-

ful materials and minerals, and the possibility of introducing

modern methods and designing new devices.

MAGNETIC SEPARATION IN ROMANIA

There is at the Centre of Technical Physics of Jassy, a

group of physicists, engineers and technicians led by

Dr. Nicolae Rezlescu which has been working on magnetic separa-

tion for more than I0 years. The preoccupations of this group

include a large range of studies concerning almost all the

various magnetic separation techniques. These studies have

materialized, up to now, in the realization of lab devices and

pilot-scale and industrial-size units I, 2, 3.As for conventional separation, a system for picking-up

tramp metal from conveyor belt-carried materials has been

designed and built. This system is equipped with a magnetic

plate with permanent magnets, suspended above the conveyor belt

and driven by a previously mounted metal detector.

At the same time, a 0.8 m long, 0.4 m diameter dry drum

magnetic separator for the food industry has been designed and

built, with an effective magnetic field range of I00 mmo

In order to obtain higher performances, larger active space

and increased magnetic action within this space, a model mag-

netic separator has been built with a toroidal air-gap 4. The

separator (Fig. I) is equipped with a toroidal magnetic circuit

with two parallel branches driven by two coaxial coils. The

feed is dispersed in the toroidal air-gap by means of a conic

distributor mounted at the top. Ferromagnetic particles from

the feed are retained on the central active element and the non-

magnetic product keeps falling, leaving the magnetically active

region through the lower holes made in the magnetic circuit.

A scraper which goes round the torus periodically sweeps the

ferrous bodies and discharges them through a region of zero

magnetic field.

In matters of high intensity magnetic separation, attention

has been focused on the application of induced roll magnetic

separators. At the request of various users, our group made a

series of studies to optimize the separation process as well as

?6 N. REZLESCU ET AL.

FIGURE i Model of magnetic separator with toroidalair gap.

MAGNETIC SEPARATION IN ROMANIA 77

the design and working parameters of the installations when

processing specific materials. The researches in this field

have materialized in the designing and manufacturing two types

of induced-roll separators, one for lab analyses and the ocher

for industrial purposes [5]. The lab separator has a 120 mm

long, IiO m diameter roll; the magnetic induction in the sep-

aration space can e continuously changed from 0.2T to 1.ST.It is designed for use in geology and chemistry laboratQries of

geology and chemistry. The ndustrial separator has four 1.0 m

long, O. Ii m rolls, working in parallel, with the magnetic

induction changing step by step between 0.2T and I.OT. It is

used in alumina plant using deferrized ash from thermal plantsas raw material.

The group from the C.T.F. of Jassy have given increasing

attention in recent times to the study of HGMS. The objective

has been to get process data for the purpose of establishing

the optimum conditions for processing specified materials as

well as establishing the optimum working and design conditions

for the ma=ufacture of in-house HGMS devices. The resulting

devices work in the longitudinal confiaration. The ferromag-netic matrices are made of 65-165 m thin wires drawed frommagnetic stainless steel. For our own lab activity and for

mineralogy and chemistry labs two types of HGMS separators.have been conceived and produced at C.T.F. of Jassy, with 150 mm

long canisters 1.0 and 4.0 capacity respectively (Fig. 2).

The electromagnets of the two separators generate magnetic

fields which can be ramped continuously between OST and 1.8T.

The coils of the electromagnets are wound after Allen’s method/6/

for the first separator, the power requirement being of 70 KVA

for the maximum field and after Chikasumi’s method /7/ for thesecond, the maximum required power being 45 KVA. At the request

of the clay industry, a prototype pilot-scale separator was

designed and constructed with canisters of 80 , capacity and

78 N. REZLESCU ET AL.

300 mm length. The maximum field was 1.8T for a power consump-

tion of 75 KVA /8/.

FIGURE 2 Laboratory HGMS separator.

MAGNETIC SEPARATION IN ROMANIA 79

Research work concerning magnetodensimetric separation (MDS)

has involved both MHS separation with magnetic fluids and MHD

separation with electroconductive fluids. In the period 1976-

1978 two model MHS separators were made at the C.T.F. of Jassy

(Khalafalla and Rosenweigh type respectively), with a view to

testing practicability of the MHS method for non-ferrous ores.

In 1979 an MHS model was conceived and made with petroleum-

based ferrofluids and saturated solutions of paramagnetic salts

being used as magnetic fluids /9/. The separator was of a

dynamic type, with the working liquid flowing through the separ-

ation space, the resolution increasing with increasing channel

length. Since the acquirement of linear air gaps longer than

I000 mm in C- or H-shaped electromagnets needs very large con-

structions and excessive power consumption, a magnetic circuit

with a toroidal air gap was realized (Fig. 3).

FIGURE 3 Magnetic circuit of the model of MHSseparator.

80 N. REZLESCU ET AL.

With this set-up one can easily obtain air gaps longer than

3,000 mmo The exit of the separation channel is divided in two

compartments, permitting the collection of two fractions from

the mixture to be separated. By separating grained mixtures of

AI- Cu, AI- glass and Cu- glass, concentrates were obtained at

first with grades exceeding 75%. The tests were continued, a

dependence being established between the efficiency and a series

of parameters such as the flow rate of the working fluid through

the separation channel, the channel height, and the character-

istic size of the particles to b.e separated.MHD separation was initially investigated at the Centre of

Technical Physics of Jassy early in 1982. Three types of MHD

separations have been studied, starting from the principles of

the three classical processes of gravity concentration: jigging

separation, ascending flow classification and horizontal flow

classification [I0]. In the MHD jigging (Fig. 4) the separa-

tion was rendered apparent by using PVC, rubber, glass, graphite

and quartz grains. A 15% NaOH solution was used as electrolyte.

The tests that were undertaken allowed for the determination

of the optimum values of the parameters influencing the MHD

jigging.

The ascending flow system was chosen for the sequential

separation (Fig. 5). The mixture to be separated, consisting

of more densimetric fractions, is introduced at the bottom of

the separation cell, forming a fluidized bed downside the elec-

trodes. By increasing step-by-step the magnetic or the electric

fields- or both simultaneously- the apparent density of the

electroconductive liquid increases, so that the liquid is able

to carry over sequentially particles of corresponding densities

from the mixture to be separated.

The closed horizontal channel system has as its main element

the separation channel (.Fig. 6), consisting of three sections:

MAGNETIC SEPARATION IN ROMANIA 81

N

FIGURE 4 Schematic of MHD jigging.

FIGURE 5 Sequential MHD separation system.

82 N. REZLESCU ET AL.

FIGURE 6 Horizontal closed channel MHD system.

section A for introducing the electrolyte and the mixture to be

separated, section B of magnetohydrodynamic action, and section

C for the removal of the separated phases. By working with

current densities of 0.3- i A/cm2, fields of 0.75- 2.0T andelectrolyte flow rates of 0.5- I m/s within a 450 m long separ-

ation channel, the stratification of certain mixtures was succeed-

ed with densities ranging between 2.5 and 7 g/cm3, in light andheavy fractions, thus obtaining concentrates with grades exceed-

ing 75% in a single step separation.

On the basis of the results obtained with the first two

systems, work was continued to produce lab analysers to

MAGNETIC SEPARATION IN ROMANIA 83

facilitate the mineralogic analyses in geological survey labor-

aries.

The closed channel MHD separation system with horizontal

flow will be rebuilt as a pilot scale prototype meant to concen-

trate coking coals as well as 0.3- 3 mm granulary non-metallic

and non-ferrous ores. Its output will exceed i t h-I, depend-ing on the processed material.

A notable contribution to the assimilation of magnetic sep-

aration in Romania has been brought by the Research Institute

for Electrotechnical Industry of Bucharest. The main activity

of this Institute has been the design and fabrication of a series

of modular dry induced-roll separators with one or two

overband magnetic separators and dry drum magnetic separators

with permanent magnets /II.

The Mining Research and Engineering Institutes of Cluj-

Napoca, Deva and Baia Mare are particularly concerned with the

introduction of magnetic separation methods in ore processing

flow sheets. The Institute of Cluj-Napoca has as its main

objective the utilization of HGMS method in clay, kaolin and

feldspar processing, a HGMS separator with a 300 mm long canister

having a 1.2 m diameter and a maximum field of 2.OT being

designed and manufactured here.

The Institute of Deva is mainly concerned with iron ore pro-

cessing f127. It optimizes and projects flow sheets, many of

these including magnetic separation. At the same time, a contin-

uous (carousel) HGMS separator has been designed and built for

use in iron ore recovery from the slimes deposited in settling

tanks.

The main concern of the Institute of Baia Mare is in non-

ferrous ore (Cu, Mn, Pb, Sn, Au, Ag) processing. Recent work

there includes MDS separation with ferrofluids, a Khalafalla lab

separator being produced for concentration tests on non-ferrous

ores.

84 N. REZLESCU ET AL.

Finally, we should mention that there are at the higher

education institutes of Jassy, Timisoara and Petrosami, research

teams working on ferrofluid based MDS separation /13, 14/;

they are mainly concerned with the theoretical aspects of MDS

separation.

REFERENCES

I. N. Rezlescu and V. Badescu, _St...Cercet. Fiz., 32, 4, 365(980).

2.. N. Rezlescu, V. Badescu, E.B. Bradu, D. Ruscanu andD. Constandache, Sty. C.erce_t. Fiz., 32, 7, 755 (1980).

3. N. Rezlescu, V. Badescu, Gh. lacob, E.B. Bradu andD. Constandache, Memoriile St. Acad. RSR, seria IV, 3, I,135 (1981).

4. N. Rezlescu, Gh. lacob, V. Badescu, E.B. Bradu andD. Constandache, Proc. II_ Conf. Magn., Jassy, 1979, 310 (1980)

5. N. Rezlescu, V. Ba’d’e’scU, Gh, lacob, D. Ruscanu,D. Constandache and E.B. Bradu, Proc_._ II_ Conf. Magn.,Jassy, 1979, 462 (1980).

6. J.W. Allen, Pr0.c. .int. .conf. Ind. Ap.p.l.._ gn...Sep., Rindge,N.J., ii (1979).

7. Y. Ishikawa and S. Chikazumi, Ja_p. J-_ApP!-phys.., I, 3,155 (1962).

8. N. Rezlescu, V. Badescu, Gh. lacob, E.B. Bradu, L. lacoband M. Constantin, proc. Ill Conf.. Magn..., Jassy, 1983, 443(1981).

9. N. Rezlescu, V. Badescu, E.B. Bradu, IEEE Trans._ Ma.gn.,MAG-17, 6, 3320 (1981).

i0. L’. "i’acoh, M. Constantin, V. Badescu and N. Rezlescu,P.ro_c- I.!! C_onf_._ Ma_gn., Jassy, 1983, 437 (1984).

ii. I. Bahrim, L. Hncu and N. Teodoresou, Pro_c._ II _Conf Magn.,Jassy, 1979, 319 (1980).

12. D.I. Ciofringeanu, The Study Of Mineral_ Processing _yMagn.etic epa[.a.t..i.on i.n Pp!y_gradient_ Field, Ph.D. Thesis,Petrosani, 1984.

13. Gh. Calu8aru, Gh. Coman, D. Zoler, C. Cotac and I. Starparu,Proc, .I.I .Conf. Magn., Jassy, 1983, 425 (1984).

14. V. lusan, L. Homorodean, I. Malaiescu and V. Muntean,Proc. Ill Conf. Man., Jassy, 1983, 431 (1984).